I'm doing work on a car audio amp and am having some trouble locating exact replacements for the output transistors. How do I determine if another transistor will work as a replacement?Do I just need to find one with equal or higher maximum ratings?The transistor in question is a KTB688. I have a few 2sa1909 transistors laying around and the ratings appear to be higher.Will this part work in place of the KTB688?Also if it will work will i need the complement to the 2sa1909 or will the complement to the ktb688 work with the 2sa1909?